For quite some time it has been recognized that various containers such as cups and particularly, containers for the dispensing of ice cream treats can be formed from various plastic materials. In addition to plastic materials, one very popular container material has been manufactured from paper products. A well known container of the above mentioned type is the so-called push-up cup which is essentially a cylindrical outer body with a movable plunger positioned on the interior thereof. A stick is attached to the interior plunger, thus permitting the user to push the contents of the push-up cup upward as it is consumed. Cups of the push-up variety have been manufactured not only from paper, but also by the well known injection molding technique. Heretofore, push-cups have not been successfully manufactured from polystyrene beads since a certain degree of strength is required over and above that afforded by the polystyrene beads. In forming cups of the steam chest variety, it has been necessary in the past for purposes of imparting adequate strength and rigidity and surface finish, to construct such cups with a rather thick sidewall and rim. As a consequence of this added sidewall thickness, it is not possible to package as much product per container as can be accomplished when the sidewall is relatively thin. Thus from an overall storage and relative strength position, a more desirable material is dictated.
Paper push-up containers do have the required strength while the paper remains in the dry condition, however, when the paper becomes saturated with an inherently wet product, it rapidly loses its strength.
Another disadvantage of the so-called steam chest molded push-up container is that, as an inherent consequence of its mode of manufacture, the external surface of its sidewall can only be decorated subsequent to the manufacture of the push-up container. The required or necessary post decoration and printing techniques are considerably slower and more expensive than the flexographic and other printing techniques which may be used to decorate various sheet material prior to incorporation into cup-like containers. As a result, the majority of steam chest molded cups on the market today do not contain a decorated exterior simply because such decoration would have to be applied after the cup is fabricated.
Also, cups and cup-like containers have been made of insulated or expanded thermoplastic materials by cutting an appropriate arcuate shaped blank from sheet stock material and forming it into a cylindrical container with techniques that are well known in the art of making paper cups and ice cream buckets. This process of container fabrication permits the container exterior sidewall to be decorated while the plastic or paper material is in sheet form and prior to the cutting of the rectangular shaped sidewall blanks. By controlling the density of such plastic sheet stock, it is possible to fabricate a container with adequate strength, rigidity and liquid impermeability and which has a considerably thinner sidewall than for example a stream chest molded cup. Also, the ease with which the exterior of the sidewall of such containers can be provided with attractive and sometimes required information by predecorating the sheet from which the sidewall blanks are formed, has made it possible for a substantial number of such containers to be decorated in a way which has proven to be quite popular in the trade.
One of the inherent disadvantages of such containers is the fabrication of the return lip on the bottom of the push-up container. This particular return lip geometry requires that the material be moved a considerable distance, thus subjecting it to tears and also cracks which reduce its peripheral strength to a marked degree. Another known type of insulated or expanded thermoplastic container which has met with some measure of commercial success and is somewhat analogous in structure to the push-up container is the one-piece seamless deep draw cup which is manufactured by the well known thermoforming process. Such cups can be formed to a very close manufacturing tolerance and with excellent stacking features, if so desired. Once again, the decoration of thermoformed deep drawn containers must be achieved subsequent to their fabrication.
As can be realized from the foregoing discussion, each of the well known types of insulated containers referred to has certain inherent advantages which make it well suited for some uses and certain limitations which make it less suited than one of the other types for other uses.
Another variation in the manufacture of push-up containers is also feasible at this time. This particular insulated push-up container combines a wide range of desirable properties, without offsetting limitations such as are found in paper cylindrical containers. This new variation of the push-up container is well suited for a wide range of applications for insulated push-up cups. The sidewall of such container can be formed from rectangular blanks, therefore, without any appreciable amount of scrap and extra expense involved in severing special shaped container sidewall blanks from a sheet or web of material. The sidewall of such push-up container may be relatively inexpensively provided with attractive, high quality decorative designs. Additionally, such cup may, if desired, be provided with a very slight taper which enhances the movement of the internally contained plunger which moves the edible product in an upward direction. Relatively inexpensive high quality push-up containers have been fabricated from rectangular shaped blanks. The sidewall of the push-up container is formed from a web of polystyrene or other thermoplastic polymeric sheet material which has a substantial degree of orientation or heat shrinkability built into the so-called machine direction of the web of material. Decorative material is applied to the oriented web of material and after printing, the web is severed into long strips, each containing the repetitive pattern of individual container blanks. The strips of material are then severed into individual container blanks which are then formed into cylindrical sleeves with the machine direction of the parent web extending circumferentially around the push-up sleeves. In the formation of the sleeve, a liquid-type lapped seam is effected by heat or solvent sealing techniques. A sleeve winding mandrel is employed to form the push-up sleeve to the desired diameter and to make the required side seam. The completed sleeve is then placed on a mandrel, if it is not formed in situ on said mandrel, and having an outer forming surface corresponding to the desired configuration of the inner surface of the container sidewall, whether such sidewall be substantially straight or tapered, such as in a cup or push-up container. A portion of the sleeve may be cantilevered over the free end of the mandrel in order to form the rim on the bottom of the push-up container or its entire bottom if so desired. The remaining portion of the sleeve may be conformed to the exterior surface of the mandrel by the application of heat. The fabrication of a one-piece push-up container according to the present invention is effective to provide a container that can be used for frozen or semifrozen food products. Of course, the container also lends itself to edible products that are not frozen but are semiliquid in consistency. The apparatus for fabricating a one-piece push-up container in accordance with the method of the present invention includes a drum mechanism that moves in an arcuate path and carries a plurality of spaced apart mandrels. Each mandrel has an external configuration that corresponds to the internal contour and configuration of the push-up container. The drum carries the attach mandrels through a series of operational subassemblies which function in timed sequence interrelationship with the mandrels to form the container of the present invention. In addition to rotating with the drum, each individual mandrel is capable of rotation about its own axis to effect the winding of cylindrically shaped sleeves from flat webbed sheet stock. With the process and apparatus of the present invention, push-up containers having exceptional properties can be fabricated at a relatively low cost and at high production speeds. Because the operation of the present apparatus is continuous in nature, it is extremely smooth in operation and achieves excellent production speeds during the manufacture of containers.
It is an object of the present invention to provide an apparatus for the manufacture of cup-like containers.
It is an additional object of the present invention to provide a machine for the manufacture of push-up containers manufactured from foamed plastic material.
These and other objects have been attained in accordance with the present invention in that a rotary machine for the manufacture of push-up containers from a thermoplastic material that shrinks in a controlled fashion under the influence of heat is provided for. It is also a feature of the present invention to provide a method and apparatus for thermally fabricating a push-up container from a rectangular blank of oriented thermoplastic material without the need for wasting any portion of the material in such blank. More particularly, it is a feature of the present invention to provide a method and apparatus for fabricating a container from a rectangular blank of oriented thermoplastic material wherein the bottom rim of the push-up container is formed substantially simultaneously with the remainder of the container.